If its the courtyard I’m thinking of, a well placed fireball can also be the most satisfying spell of the game.
My favourite spell for Shadowheart was always spirit guardians. Partly just because it was funny to watch her dashing around the map, mopping up weaklings.
Yeah it seems super buggy. I had her in my party the whole time, did her quest etc, but she didn’t offer any help. Didn’t think anything of it until I reloaded the save to see some more endings, and all of a sudden she’s like “have some harpers!”